Medsafe will not change its advice on strong medicines used for treating stomach acid, even after research showed they pose additional risk of a kidney disorder.

A University of Otago study has found proton pump inhibitors – designed to reduce gastric acid production – can increase the risk of interstitial nephritis, New Zealand Doctor reported.

Interstitial nephritis makes filters in the kidneys swell, causing problems with the way they work and can be temporary or long lasting.

The temporary form of the kidney disorder was most often caused by side effects of certain drugs.

Medsafe, the New Zealand safety authority for medicines and medical devices, said the known frequency of interstitial nephritis was between one in 1000 and one in 10,000 – in medical terms it was "rare".

"The same rate was found in this [University of Otago] study – 1.2 in 10,000," Medsafe said.

Data sheets provided with the drugs and advice given to prescribers already acknowledged the rate of the kidney condition found in the study, Medsafe said.

Pharmacoepidemiologist Lianne Parkin said the excess risk was low in absolute terms, but important from a population perspective, because many people used proton pump inhibitors.

The drugs in the study were extremely safe for the vast majority of users, Parkin said.

Medsafe said anyone worried about using the drugs should seek appropriate medical advice.

"Prescribers should be aware of this increased risk of interstitial nephritis (compared to not taking the medicine), and for patients to seek appropriate advice before using these medicines."